Valve Guides

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6

69Chrgr

Charger/Cuda
Joined
Jan 29, 2007
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Location
Midlothian, Texas
Would bad or "leaking" valve guides cause blow by and high crankcase pressure? I have a set of Edelbrock Magnums on my 408 and it just blew the front seal between the oil pan and the timing chain cover out on my 11.90 pass. How would you check for this? Any help appreciated.
 
High crankcase pressure is due to blow-by past the rings or a damaged piston.

Run a leak down test.
 
No, because they are not open to the chamber when the pressure builds. More like rings. Do a leak down on it.
 
You're right. Not real sure how to use the leakdown tester, but you can hear air pressure going into the crankcase. Its consistent with all the cylinders. I used chrome moly rings. Could it be that it takes them for ever to seat? I hate to tear down a really strong motor.
 
Are your breather caps on your valve covers good?I have Mopar Performance valve covers on my 383.I turned it 7500 RPM one day and blew out the valley pan under the intake.Looked at my breathers caps and they were not opened all the way up from the factory.I replaced the valley pan and opened up the breathers and it was OK after that. Jim
 
It seems to do this with or without breathers. I have 3 open element breathers. I just read on another thread that you have to use a special honing process when using chrome moly rings. The motor probably only has about 300 miles on it, with about 20 1/8th mile trips and 15 1/4 mile trips. Compression is consitstent on all 8 cylinders @ 180 psi, but yeah I know I can have good compression and still have blow by. I'm just getting frustrated.
 
How many miles are on it? Are there any pics showing the cylinders during assembly? before you ran it? You have two gages. One is "line pressure" of the air system of the shop. The other reads the pressure that is being maintained in the cylinder being tested. The difference is the leakage. A difference of more than 8% in a fresh engine is a problem. So how many miles on yours?
 
The rings didnt seat properly. The questions now become "why?" and "will they ever?" So what did the hone job look/feel like?
 
The hone job had a very nice crosshatch pattern. Would it help if I ran a really thin oil? I hate to start all over again.
 
The problem is not a crosshatch, but how rough a finish was left. If the crosshatch was very distinct, and rough enough to catch your fingernail, it was too rough. It also could be that when it was assembled the cylinders and rings were soaked with engine oil. I think one of two things may happen: They may seal over time and lighter oil will help that. Or, the rings were trashed by the sharp edges of the rough surface (we are talking on the microscopic level) and they are actually worn too much already to seat properly. The right surface finish is very important with moly faced rings. It should be almost a polished look, with some hone marks visible but not "feelable". And rings should be assembled with minimal oil. I use WD40, some use graphite powder, some isntall them dry. When done properly a set of file-to-fit molys will be 75% seated after the cam break in. See the pic I attached... crosshatch is visible, but the surface loks polished enough to reflect well.

001.jpg
 
Thanks for your informative reply. Yes, I used oil in the assembly of the engine. I think you just nailed it. Looks like I really goofed up. I guess I can try lighter oil, but the damage is probably done. About right for my luck. What oil would you suggest?
 
Moper, I called Indy Cyl. Head and discussed this issue with them, and it looks like I need to take the motor back down. Yes a pain, but they said I could just have the block rehoned for a new set of rings. I had the block bored .030 over. It would be great if I didn't have to bore the block again. What's your thought?
 
LOL... Indy?? they have the same issues..lol. that's funny as hell... :D
I think the re-hone will be fine. but, it does require the block to be stripped bare, so it can be properly cleaned afterwords. So order cam bearings and freeze plugs for it. Also, MAKE SURE the shop you chose has the proper tooling to do the job right... They need the torque plate, the usual coarse stones, fine stones, and a brush hone to ge the plateau finish. During assembly, after the block is washed with soap and water and brushes, wipe each bore carefully with solvent in the direction of the hone marks. Keep doing this until the towel comes out clean. Squirt a little 30wt oil on the skirts and pin areas, and then just WD40 on the rings and ring lands. Then install it. It should be fine. No synthetics until there's 1000 miles on it.
 
O.k. Moper, help me out here. I just performed a leakdown test with my neighbors leakdown tester. It didn't have any instructions, but this is what I got on all 8. Also, I was told the slight air I heard going into the crankcase was normal as it is passing through the ring endgaps. Anyway, this is how it read:
On TDC, pulled plugs, hooked up adapter into plughole, plugged tester in and when I turned the valve to pressurize with shop air, the left guage would go up to 40 PSI when the right gauge needle hit set, or 0%. Leaving it there, it did not move. The left gauge had KPa and PSI. I went by PSI. As soon as I would pressurize the cylinder, the right gauge would start moving quickly, going from 100%(red) to 0%(green) when it got to 40 PSI. All eight cylinders, same thing. Is this bad?
 
O.k. Moper, now that I got on the internet and finally figured out you have to pressurize the guage, THEN hook up the adapter from the plughole, yeah, I'd say about 25% leakage. Oh well. This sucks.
 
69, sorry, I was busy last night and only on for a second whenI got home. Yes. You will almost always hear a very slight amount of air, not always from the engine but rather the fittings on the gage set. In any event, 25% is bad. (even for Indy...) The good news is you know why, and overall, it's not a catastrophic failure. The bill will be in the hundreds, plus a little time. That's not terrible.
 
Thanks very very much for your time and expertise moper. I slept on it and it gives me a good excuse to send my Eddies on over to Shady Dell. Thank you so much!
 
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